METHOD OF ELECTROMAGNETIC FLAW DETECTION IN MULTISTRING WELLS AND ELECTROMAGNETIC WELL FLAW DETECTOR Russian patent published in 2014 - IPC E21B47/08 G01N27/90 G01B7/16 

FIELD: mining.

SUBSTANCE: method of electromagnetic flaw detection in multistring wells includes measurement of auto-inductance EMF induced in a coil by eddy currents induced in investigated metal barriers by process of electromagnetic field decline induced by current pulses of coil excitation. To each of receiving-exciter coil a pulse group of fixed length from the range of 0.1-1000 ms is supplied individually, magnetising in sequence all metal barriers starting from the nearest. Length of pulses increases for each subsequent metal barrier. Obtained data are stored and processed by comparison to model data. By the processing results presence of defects in metal barriers is judged. Electromagnetic well flaw detector contains a housing, coils arranged along the axis of the device, electronics module, at least two receiving-exciter coils, each of them consists of receiving and exciter coils with common core. Receiving-exciter coils are made of different size spaced apart on the device axis at a distance not less than the length of larger receiving-exciter coil.

EFFECT: improving accuracy and validity of detection of existence and location of transverse and longitudinal structural defects of well and underground equipment both in magnetic and non-magnetic first, second and subsequent metal barriers.

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